Page 39 - Advances in Textile Biotechnology

18 Advances in textile biotechnology

presented higher tensile strength and lower felting and pilling, along with
lower weight loss, which indicates that the new developed enzyme only
hydrolyzed the cuticle layer of wool (Araújo et al., 2009). This new high
molecular weight subtilisinE-VPAVG 220 represents a breakthrough in the

wool-finishing process, promising to be an alternative to the traditional
highly polluting chlorine/Hercosett treatment. In addition, this enzyme can
be included in new detergent formulations that can be used to wash all types
of garments, including silk and wool.
Finally, the cost of enzyme production is a major obstacle to the success-
ful application of proteases in textile industry. Protease yields have been
improved by screening for hyperproducing strains and/or by optimization
of the fermentation medium. Strain improvements either by conventional
mutagenesis or recombinant-DNA technology have been useful in improv-
ing the production of proteases. Most, if not all, Bacillus detergent proteases
currently are recombinant, genetically engineered products, secreted by
overproducing strains.

1.4.5 Lipases/esterases
Esterases represent a diverse group of hydrolases that catalyze the cleavage
and formation of ester bonds. They are widely distributed in animals, plants
and micro-organisms. These enzymes show a wide substrate tolerance and
high regio- and stereospecificity, which make them attractive biocatalysts

for the production of optically pure compounds in fi ne-chemicals synthesis.
They do not require cofactors, are usually rather stable and are even active
in organic solvents (Bornscheuer, 2002). Two major classes of hydrolases
are of most importance: lipases (triacylglycerol hydrolases) and ‘true’ este-
rases (carboxyl ester hydrolases).
Most of the alterations introduced in esterases/lipases address detergent
use and surfactant compatibility. Oxidative stability, important for proteases
and amylases, is not the major interest in the case of lipases, since many
lipases are already stable in oxidative reagents. In Candida antarctica B
lipase the exchange of Met at position 72 by Leu resulted in an increased
stability towards oxidation by peroxyoctanoic acid (Patkar et al., 1998). A
few studies also report the substitution of Met in lipases from Pseudomonas
sp. by other residues to prevent the inactivation by oxidation in oxidative
detergents (Van der Laan et al., 1994).
Regarding calcium independency, Simons et al. (1999) engineered S.
hyicus lipase by site-directed mutagenesis. Based on sequence alignment to
other lipase sequences, from P. glumae for example, the aspartate residues

in position 354 and 357 were identified as calcium-binding ligands and
replacement of Asp357 by a glutamate decreased the affinity for calcium

ions by 30-fold. Introduction of a lysine, an asparagine, or an alanine at
position 357 and of a lysine or an asparagine at position 354 resulted in

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